{"api_version":"1","generated_at":"2026-10-25T16:27:59+00:00","cve":"CVE-2026-98441","urls":{"html":"https://cve.report/CVE-2026-98441","api":"https://cve.report/api/cve/CVE-2026-98441.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-98441","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-98441"},"summary":{"title":"net/sched: act_ct: avoid modifying shared unconfirmed ct entry","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_ct: avoid modifying shared unconfirmed ct entry\n\nIn a case where skb with an unconfirmed ct entry gets cloned, we may\nend up processing both again but with different sets of extensions.\n\nThe series of events:\n\n 1. The first clone wants to commit and runs the helpers wiring up\n    the extension pointer into the expectation list.\n 2. Then it looses the confirmation keeping the entry unconfirmed.\n 3. Second clone now wants to commit labels or run NAT and adds the\n    new extension for that breaking the pointer in the expectation\n    list causing UAF on the destruction path later.\n\nWhile this is possible to trigger, there should be no practical\nnetwork pipeline where we need to process both clones without\nmodifications in the same zone.  So, let's just reset the entry in\ncase for some reason we got an skb with a shared one.  This doesn't\naffect any known use cases, but avoids any potential problems with\nsharing and modification of the unconfirmed ct entry.\n\nUnlike openvswitch module, act_ct allows for NAT without commit.\nChanging that would be a uAPI break.  So, act_ct needs to reset on NAT\nregardless of the commit flag to avoid reallocation of the extension\nspace.  This, however, doesn't really change the picture for sensible\nnetworking cases as there should be no need to run the same packet\ntwice (before and after the clone) through conntrack without packet\nheader or zone changes and without commit.\n\nThe fixes tag points to the introduction of helpers, since that's the\nmain UAF trigger for the sharing.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-10-18 16:16:54","updated_at":"2026-10-24 14:16:41"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"7.8","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"7.8","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","data":{"baseScore":7.8,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/b097d9d7a5b09c8ec5c4c1a08e35ac5a66b06b44","name":"https://git.kernel.org/stable/c/b097d9d7a5b09c8ec5c4c1a08e35ac5a66b06b44","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/4a04ed91575819fb1859311113e95700b709bec7","name":"https://git.kernel.org/stable/c/4a04ed91575819fb1859311113e95700b709bec7","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/f85009dfcd65e5969526b0db7a49b5413746e630","name":"https://git.kernel.org/stable/c/f85009dfcd65e5969526b0db7a49b5413746e630","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/2b783c562c3238ff50c34fd7a72a735c9cc73d9a","name":"https://git.kernel.org/stable/c/2b783c562c3238ff50c34fd7a72a735c9cc73d9a","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/c812bb4aea13d385d048b5b24756aee2edf6f99e","name":"https://git.kernel.org/stable/c/c812bb4aea13d385d048b5b24756aee2edf6f99e","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-98441","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98441","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected a21b06e7319129994f339ed47f512bbe57b77f5b c812bb4aea13d385d048b5b24756aee2edf6f99e git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected a21b06e7319129994f339ed47f512bbe57b77f5b 2b783c562c3238ff50c34fd7a72a735c9cc73d9a git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected a21b06e7319129994f339ed47f512bbe57b77f5b 4a04ed91575819fb1859311113e95700b709bec7 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected a21b06e7319129994f339ed47f512bbe57b77f5b b097d9d7a5b09c8ec5c4c1a08e35ac5a66b06b44 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected a21b06e7319129994f339ed47f512bbe57b77f5b f85009dfcd65e5969526b0db7a49b5413746e630 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.2","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.2 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.160 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.112 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.55 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.9 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"98441","cve":"CVE-2026-98441","epss":"0.001680000","percentile":"0.057250000","score_date":"2026-10-21","updated_at":"2026-10-22 00:15:10"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["net/sched/act_ct.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"c812bb4aea13d385d048b5b24756aee2edf6f99e","status":"affected","version":"a21b06e7319129994f339ed47f512bbe57b77f5b","versionType":"git"},{"lessThan":"2b783c562c3238ff50c34fd7a72a735c9cc73d9a","status":"affected","version":"a21b06e7319129994f339ed47f512bbe57b77f5b","versionType":"git"},{"lessThan":"4a04ed91575819fb1859311113e95700b709bec7","status":"affected","version":"a21b06e7319129994f339ed47f512bbe57b77f5b","versionType":"git"},{"lessThan":"b097d9d7a5b09c8ec5c4c1a08e35ac5a66b06b44","status":"affected","version":"a21b06e7319129994f339ed47f512bbe57b77f5b","versionType":"git"},{"lessThan":"f85009dfcd65e5969526b0db7a49b5413746e630","status":"affected","version":"a21b06e7319129994f339ed47f512bbe57b77f5b","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["net/sched/act_ct.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"6.2"},{"lessThan":"6.2","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.160","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.112","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.55","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.9","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.160","versionStartIncluding":"6.2","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.112","versionStartIncluding":"6.2","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.55","versionStartIncluding":"6.2","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.9","versionStartIncluding":"6.2","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3","versionStartIncluding":"6.2","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_ct: avoid modifying shared unconfirmed ct entry\n\nIn a case where skb with an unconfirmed ct entry gets cloned, we may\nend up processing both again but with different sets of extensions.\n\nThe series of events:\n\n 1. The first clone wants to commit and runs the helpers wiring up\n    the extension pointer into the expectation list.\n 2. Then it looses the confirmation keeping the entry unconfirmed.\n 3. Second clone now wants to commit labels or run NAT and adds the\n    new extension for that breaking the pointer in the expectation\n    list causing UAF on the destruction path later.\n\nWhile this is possible to trigger, there should be no practical\nnetwork pipeline where we need to process both clones without\nmodifications in the same zone.  So, let's just reset the entry in\ncase for some reason we got an skb with a shared one.  This doesn't\naffect any known use cases, but avoids any potential problems with\nsharing and modification of the unconfirmed ct entry.\n\nUnlike openvswitch module, act_ct allows for NAT without commit.\nChanging that would be a uAPI break.  So, act_ct needs to reset on NAT\nregardless of the commit flag to avoid reallocation of the extension\nspace.  This, however, doesn't really change the picture for sensible\nnetworking cases as there should be no need to run the same packet\ntwice (before and after the clone) through conntrack without packet\nheader or zone changes and without commit.\n\nThe fixes tag points to the introduction of helpers, since that's the\nmain UAF trigger for the sharing."}],"metrics":[{"cvssV3_1":{"baseScore":7.8,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"scenarios":[{"lang":"en","value":"AV:L - RTM_NEWTFILTER over NETLINK_ROUTE enters rtnetlink_rcv_msg()→tc_new_tfilter()→tcf_ct_init(); matching packets then reach the patched tcf_ct_act() through tcf_action_exec(), and no remote protocol message alone creates the required clone/commit graph.\nAC:L - The attacker controls the cloned skb branches, helper traffic such as a TFTP RRQ, NAT/commit actions, and competing same-tuple confirmations; repeated concurrent submissions can produce the nf_conntrack_confirm() loser state without an independent victim condition.\nPR:L - rtnetlink_rcv_msg() requires CAP_NET_ADMIN in sock_net(skb->sk)->user_ns, not init_user_ns; an unprivileged user can obtain this capability with a user and network namespace and create the required tc actions.\nUI:N - After creating the tc/bridge topology, the attacker sends the packets that drive tcf_ct_act() and later nf_ct_remove_expectations(); no victim action is required.\nS:U - The stale conntrack-extension pointer and subsequent hlist_del_rcu() write affect the same host kernel authority executing tcf_ct_act(); this is ordinary kernel compromise rather than a VM, IOMMU, or other scope-boundary escape.\nC:H - nf_ct_ext_add() can free or move ct->ext after nf_ct_expect_insert() stored exp->lnode.pprev inside the old nf_conn_help; this groomable kernel-heap UAF can corrupt sensitive objects and enable arbitrary kernel-memory disclosure.\nI:H - During nf_ct_remove_expectations(), hlist_del_rcu() executes WRITE_ONCE(*exp->lnode.pprev, exp->lnode.next) through the dangling pointer into reused heap memory, enabling control-bearing object corruption and code execution.\nA:H - The stale pprev write during expectation teardown can corrupt freed or reused slab memory and cause an oops or panic, and the attacker can repeatedly create and destroy affected conntracks to trigger it."}]}],"providerMetadata":{"dateUpdated":"2026-10-24T14:08:49.686Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/c812bb4aea13d385d048b5b24756aee2edf6f99e"},{"url":"https://git.kernel.org/stable/c/2b783c562c3238ff50c34fd7a72a735c9cc73d9a"},{"url":"https://git.kernel.org/stable/c/4a04ed91575819fb1859311113e95700b709bec7"},{"url":"https://git.kernel.org/stable/c/b097d9d7a5b09c8ec5c4c1a08e35ac5a66b06b44"},{"url":"https://git.kernel.org/stable/c/f85009dfcd65e5969526b0db7a49b5413746e630"}],"title":"net/sched: act_ct: avoid modifying shared unconfirmed ct entry","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-98441","datePublished":"2026-10-18T15:14:51.664Z","dateReserved":"2026-09-25T10:25:14.349Z","dateUpdated":"2026-10-24T14:08:49.686Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-18 16:16:54","lastModifiedDate":"2026-10-24 14:16:41","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":1.8,"impactScore":5.9}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"98441","Ordinal":"1","Title":"net/sched: act_ct: avoid modifying shared unconfirmed ct entry","CVE":"CVE-2026-98441","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"98441","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_ct: avoid modifying shared unconfirmed ct entry\n\nIn a case where skb with an unconfirmed ct entry gets cloned, we may\nend up processing both again but with different sets of extensions.\n\nThe series of events:\n\n 1. The first clone wants to commit and runs the helpers wiring up\n    the extension pointer into the expectation list.\n 2. Then it looses the confirmation keeping the entry unconfirmed.\n 3. Second clone now wants to commit labels or run NAT and adds the\n    new extension for that breaking the pointer in the expectation\n    list causing UAF on the destruction path later.\n\nWhile this is possible to trigger, there should be no practical\nnetwork pipeline where we need to process both clones without\nmodifications in the same zone.  So, let's just reset the entry in\ncase for some reason we got an skb with a shared one.  This doesn't\naffect any known use cases, but avoids any potential problems with\nsharing and modification of the unconfirmed ct entry.\n\nUnlike openvswitch module, act_ct allows for NAT without commit.\nChanging that would be a uAPI break.  So, act_ct needs to reset on NAT\nregardless of the commit flag to avoid reallocation of the extension\nspace.  This, however, doesn't really change the picture for sensible\nnetworking cases as there should be no need to run the same packet\ntwice (before and after the clone) through conntrack without packet\nheader or zone changes and without commit.\n\nThe fixes tag points to the introduction of helpers, since that's the\nmain UAF trigger for the sharing.","Type":"Description","Title":"net/sched: act_ct: avoid modifying shared unconfirmed ct entry"}]}}}